Types Of Membrane Modules Research Articles

Gravity-driven membrane reactor for decentralized wastewater treatment: Comparison of reactor configuration and membrane module

Gravity-driven membrane (GDM) filtration is an attractive option for decentralized wastewater treatment due to lower energy consumption. However, insufficient information is available on the design factors of GDM reactor. In this study, we investigated the impacts of membrane aeration, types of membrane modules, and biocarrier deposition onto the membrane on water quality and membrane performance of GDM reactors. In detail, the membrane air diffuser located inside the granular activated carbon (GAC)-biofilm zone had benefit for mass transfer of dissolved oxygen and achieving co-existence of anoxic and aerobic conditions in the reactor, leading to higher removal efficiencies for organics (93.8–94.6 %), nitrogen (38.2–47.2 %) and phosphorus (31.9–57.7 %), compared to the air diffuser located outside the GAC zone (90.3 % for organics, 25.3 % for nitrogen and 7.0 % for phosphorus). In addition, the inside-out ceramic hollow fibre membrane showed ∼150–200 % higher fouling resistance (mainly cake resistance) due to greater biopolymer deposition compared to the outside-in polymeric hollow fibre membrane. However, for the outside-in flat sheet configuration, the ceramic and polymeric membranes showed comparable fouling resistance. The deposition of GAC particles on the membrane surface as secondary layer could improve permeate water quality, but at the expense of an increase in irremovable fouling.

Facile metal-ion infiltration into polyimide membranes with coordination crosslinking for efficient gas separation

We report a facile metal-ion infiltration method for engineering the properties of 6FDA-DAM:DABA (6FDA: 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, DAM: 2,4,6-trimethyl-1,3-diaminobenzene, DABA: 3,5-diaminobenzoic acid; referred to as 6FDD) polyimide membranes. The 6FDD polyimide membrane samples were simply immersed in metal ion (copper, zinc, and cobalt) solutions of various concentrations (1 and 10 wt%) to obtain metal-ion-infiltrated 6FDD membranes. The metal ions and the carboxylate group of the 6FDD polyimide form a coordination bond, which can increase the d-spacing between the inter-polymer chain distances and reduce polymer chain mobility. The coordination between the metal ion and the carboxylated polymer chain enhances the mechanical properties of the polyimide membranes. The metal ion coordination provides not only increased stiffness but also high resistance to the breaking point under elongation. The metal ions were distributed uniformly across the entire 6FDD membrane without any noticeable defects, which indicated the effectiveness and simplicity of the proposed method, which can be applied to versatile membrane module types and conformations. The metal-ion infiltrated 6FDD membrane exhibited improved gas permeability compared to that of the pure 6FDD membrane because of the enhanced diffusivity coefficient resulting from the increased d-spacing. Particularly, the metal-ion-infiltrated 6FDD membranes exhibited significantly higher plasticization resistance because of a decrease in the normalized CO2 permeability at 750 psi compared to that of the pure 6FDD membrane. For example, the normalized CO2 permeability of the 10 wt% copper-ion-infiltrated 6FDD membrane increased by 120% but that of pure 6FDD membrane increased by 315%. This was because the metal–carboxylate group coordination strongly prevented relaxation of the polymer chain when it was exposed to plasticizing gases at high gas feed pressures.

Boosting electron transfer in Cu2O@PDA hollow fiber membranes to decompose oxytetracycline under visible light with persulfate

In this study, a polydopamine (PDA)-functional hollow fiber membrane (HFM) modified by Cu2O (Cu2O/PDAHFM) was developed via photocatalysis coupled persulfate activation for oxytetracycline (OTC) degradation. It is found that PDA facilitates electron transfer and therefore promotes OTC degradation, achieving 96% removal efficiency. The quenching experiments and electron paramagnetic resonance (EPR) experiments demonstrated that •SO4−, •OH, •O2−, 1O2, and h+ contributed to the OTC removal. Based on intermediates identified by liquid chromatograph mass spectrometer (LC-MS), three possible degradation pathways of OTC were proposed. The toxicity of intermediates was evaluated by using Toxicity Estimation Software Tool (T.E.S.T.). Moreover, the Cu2O/PDAHFM can achieve more than 80% removal of OTC after 6 cycles, demonstrating the reusability of the catalyst. In addition, flow reactors with two types of membrane modules for continuous wastewater were constructed, and computational fluid dynamics (CFD) was used to simulate the mass transfer and degradation processes to compare the two reactors for degrading contaminants. This work provides deep insight into the mechanisms of photocatalysis coupled with persulfate activation for OTC degradation and an alternative method for designing wastewater treatment devices.

Membrane Unit for Integrated Gas Separation – Membrane Bioreactor (GS-MBR) System

One of the research directions of renewable energy sources is the production of biohydrogen from the dark fermentation of organic matter. During this fermentation process, since hydrogen is produced along with a complex mixture of other gases and vapors, hydrogen gas requires further purification. One relatively easy solution to this problem might be the utilization of gas separation membrane modules given their low energy consumption, simple operation and ease of upscaling. In this work, hollow fiber (HF) membranes based on polyetherimide (PEI) were developed and tested. HF membranes were spun from a polymer solution of PEI using the wet phase inversion process into a water bath using a pilot-scale spinning device. Gas transport measurements showed that membranes exhibited permeances of between 9.3 and 19.2 GPU with CO2/H2 selectivities within the range of 3.3 - 5.6. Morphology studies showed regular shapes resembling hollow fibers with outer diameters within the range of 250-320 microns, depending on various parameters of the spinning process. The best performing membranes were selected and a morphological analysis carried out. Selected fibers were incorporated into two types of membrane modules. One type was a laboratory-scale membrane mini-module used for preliminary tests, while the other membrane module was designed for the treatment of larger amounts of biohydrogen. Two types of laboratory-scale membrane separation units were constructed. For laboratory use, the low-pressure unit proved more accurate regulation to match the fermenters performance with the separation unit in comparison with the high-pressure one.

Unravelling temperature-dependent fouling mechanism in a pilot-scale anaerobic membrane bioreactor via statistical modelling

Operational temperature is one of the most vital factors that profoundly affect membrane fouling during anaerobic membrane bioreactor operation. This study uncovered the temperature-dependent fouling mechanism in a pilot-scale anaerobic membrane bioreactor treating real municipal wastewater at ambient temperature seasonally fluctuating from 35 to 5 °C. It showed that compared to time accumulation effect of fouling layer, temperature played a more profound role on influencing membrane fouling. Low temperature caused severe membrane fouling by affecting the release of proteinous soluble microbial products (SMP) and extracellular polymeric substances (EPS) and the abundance of related microbial community structure, like Proteobacteria, Firmicutes, Bacteroidetes and Chloroflexi. The path analysis model established in this study, which was statistically significant at 5% level, revealed that temperature could substantially affect SMP and EPS, especially proteinous SMP (β = −0.94, p < 0.01), and thus indirectly influence total fouling rate, since SMP and EPS had significant influence on total fouling rate (p < 0.05). A temperature-based model (R2 > 0.95) was successfully developed in this study for predicting membrane fouling development over the seasons. The output of these two models varied with the type of membrane module. As calculated from the path coefficients, the influence of temperature on the total fouling rate of polymeric membrane (0.70) was greater than that on the total fouling rate of ceramic membrane (0.56). The regression coefficients of the formula obtained from the temperature-based model using the TMP results of polymeric membrane were around twice as large as those obtained from the model using the TMP results of ceramic membrane. These results suggested that ceramic membrane had better anti-fouling property, probably due to its chemical and thermal stability, hydrophilic surface, and well-organized pore structure, as confirmed by the resistance-in-series analysis and excitation-emission matrix (EEM) analysis of the foulant layer.

Characterization of a New Flat Sheet Membrane Module Type for Gas Permeation

AbstractModern high‐performance flat sheet gas separation membranes exhibit high permeances as well as high selectivities, e.g., for CO2 separation. Novel membrane modules are desirable to transfer the intrinsic membrane performance to the process. The introduced module implements countercurrent flow, which allows for the best utilization of the required driving force, provided concentration polarization and pressure drops can be kept at bay. As such, it is different from established flat sheet modules for gas separation. The design features allow for straightforward scaling and easy adjustment to other operating conditions. During module development equation‐oriented modeling, computer‐aided engineering design and application of computational fluid dynamics for flow optimization were integrated. The prototype was investigated in a pilot plant. The experimental results reflected the simulation predictions and proved the validity of the module concept.

Development of hollow fiber reverse osmosis membranes and modules

Perspectives of the hollow fiber reverse osmosis membranes and modules development have been analysed. Comparative analysis with other types of membrane modules and tentative calculation of module’s design considering the hydrodynamic parameters of separation has been made.

A Review of Post-combustion CO2 Capture Technologies from Coal-fired Power Plants

Reducing CO2 emissions has become a worldwide research topic. Of all the sources of CO2 emissions, power plants burning fossil fuels, especially coals, account for a very large portion. For CO2 capture from existing coal-fired power plants, post-combustion technology is thus far considered the most viable method due to its “end-of-pipe” characteristic. Chemical absorption or scrubbing process is currently the technology most likely to be implemented in the near future but rather energy-intensive. Membrane-based CO2 separation process in recent years appears to be a competitive substitution for conventional chemical absorption technology. This paper reviews the basic process designs of chemical absorption and membrane-based separation processes for CO2 capture, as well as corresponding optimization methods including optimizing operational parameters, process modifications, membrane module types and so forth. In addition, some energetic and economic estimates from other researchers for these two CO2 capture technologies are summarized. It is found that membrane-based separation process does not possess obvious advantage over MEA-based chemical absorption process at the typical 90% CO2 capture degree in terms of both energy consumption and cost. Therefore, various optimization methods have not changed the fact that CCS technology will lay more burdens on power plants unless they can get enough allowances from government. In recent years, hybrid system with the target of utilizing more than one single capture technology seems to be new direction from the perspective of capture process design. However, it still needs to be further investigated.

Simulation of CO2 absorption by solution of ammonium ionic liquid in hollow-fiber contactors

Membrane-based chemical absorption of CO2 from gas mixtures containing CO2 using tetramethylammonium glycinate solution was studied in this work. The absorption media studied in this work involves a porous membrane contactor which is utilized as a physical barrier for contacting feed gas stream and the chemical solvent. The considered membrane module type was hollow fiber. The equations of concentration for both CO2 and solvent were derived and solved numerically using computational fluid dynamics (CFD) approach. The equations were solved in two dimensions and in cylindrical coordinate, i.e. axial and radial directions in order to obtain the concentration and mass transfer flux of CO2 and solvent in the hollow-fiber contactor. Both convection and diffusional mass transfers were taken into account in the simulations. The findings of CFD simulation demonstrated that as the flow rate as well as the concentration of the absorbent increased, the CO2 removal from gas mixture enhanced; while, the enhancement of gas flow rate declined the removal rate of CO2 in the contactor. The proposed simulation method revealed to be capable of predicting CO2 capture from gas mixtures in membrane contactors.

Effect of Solution Flow Pattern on Mass Transfer in Baromembrane Separation of Industrial Solutions and Effluents

The results of experimental research on hydrodynamics of solution flow in membrane channel are reported. Response curves correlating flow pattern with solution flow rate, pressure, and type of membrane module are obtained. A theoretical analysis of the research results is made with a description of the response curves using criterial equations that correlate empirical coefficients with solution flow rate in the channel, pressure, and type of membrane elements.

Hollow fiber membrane process for SO2 removal from flue gas

AbstractBACKGROUNDIn this study, a polymeric membrane process was investigated to avoid the poisoning of CO2 sorbents with SO2 during the carbon capture and separation (CCS) process. Two types of hollow fiber composite membranes were prepared using poly(ether‐b‐amide) (PEBAX) and cellulose acetate (CA) as composite materials.RESULTSBoth of the composite membranes exhibit a trade‐off between the pure gas permeance and the ideal selectivity. The PEBAX1657/PEI exhibited higher permeance than CA/PES due to the morphology of the substrate and the effects of the coating material. A mixed‐gas separation experiment investigated the SO2 removal efficiency and the CO2 loss ratio. The SO2 removal efficiency and CO2 loss ratio were found to be positively correlated with the permeance of the gas components. A multi‐stage membrane process was designed to reduce the CO2 loss ratio with a 90% removal efficiency of SO2. Compared with a single‐stage process, the CO2 loss ratio was decreased by up to 16.1%, and the membrane area was estimated at 18.1 m2 for the multi‐stage process.CONCLUSIONA multi‐stage membrane process was designed using different types of membrane modules to decrease CO2 loss ratio without sacrificing SO2 removal efficiency. © 2014 Society of Chemical Industry

Theoretical and Experimental Investigations of Flat Sheet Membrane Module Types for High Capacity Gas Separation Applications

AbstractGas permeation is increasingly considered for high capacity applications. This contribution discusses the commonly employed membrane module types for flat sheet membranes and suggests a new module concept. The applications considered are the separation of CO2 from flue gas and hydrocarbon dewpointing of natural gas. Rigorous models for predicting the operating performance of the module types are described. Pilot plant experiments were conducted to validate the model for envelope type modules. Simulation studies were carried out to predict the performances of the different module types for the two examples and assess their advantages and disadvantages.

The hybrid process TiO2/PAC: performance of membrane filtration

In investigations concerning the photocatalytic degradation by TiO(2) usually filter discs with a pore size of 0.22 mum and 0.45 mum are used for the removal of photocatalyst particles in aqueous suspensions. In this study the effective rejection of suspended particles by microfiltration in different types of membrane modules and with different membrane materials was investigated. Furthermore, Powdered Activated Carbon (PAC), which can be used to gain an increase in photocatalytic degradation rates, was investigated concerning its influence on the membrane performance. It is shown that by membrane filtration with a pore size above 0.1 mum, irrespective of the experimental conditions, no complete removal can be achieved. However, UV irradiation was found to improve the removal efficiency for all types of tested membrane materials. The addition of PAC also led to a higher performance of membrane filtration with regard to particle rejection. In long-term experiments with a hollow fibre membrane module in the presence of PAC a five-fold decrease of TiO(2) particles in the permeate could be proven. Besides, it was shown that added PAC can shield the membrane regarding the abrasivity of TiO(2), which could otherwise lead to the destruction of the membrane. Therewith PAC exhibits another crucial advantage besides its synergetic effect in photodegradation.

One-step dynamic assembly of polyelectrolyte complex membranes

During the past decades, layer-by-layer (LbL) assembly technique based on electrostatic adsorption of oppositely charged polyelectrolytes (PEs) has been one of the most frequently utilized processes for assembling ultra-thin film. However, LbL process is also recognized as a time-consuming process, especially for assembly of dense membranes. In this paper, a one-step dynamic assembly based on electrostatic adsorption was developed to prepare the PE complex membranes. The chitosan (CS), used as a model polycation, was dynamically deposited on a hydrolyzed polyacrylonitrile (PAN) support membrane with negative charges under a selected pressure to form a PE complex membrane for pervaporation separation of water–ethanol mixture. Compared with traditional dip-coating method, this new assembly process could offer some advantages such as the formation of selective layer with dilute solution, easily used for different membrane module types and suitable for large scale applications. The assembly conditions such as dynamic pressure, CS molecular weight, and CS concentration were investigated. The appropriate conditions for assembly were: dynamic pressure, 0.2 MPa; CS molecular weight, 82,000; and CS concentration, 0.5 wt.%. In the case of pervaporation of 95 wt.% ethanol/water mixtures, the separation factor and the permeate flux of the CS polyelectrolyte complex membranes were 422 and 230 g/(m 2 h) (60 °C), respectively. The cross-linking treatment with glutaraldehyde and sulfuric acid were subsequently performed. It was found that the separation performance was improved by the cross-linking treatment. Finally, inner skin hollow fiber PE complex membranes were also successfully explored using one-step dynamic assembly for pervaporation dehydration. The proposed process will offer a new approach to obtain a relatively integrated PE complex membrane.

CO2 Removal from CO2−CH4 Gas Mixture Using Different Solvents and Hollow Fiber Membranes

Commercial hollow fiber membrane modules have been investigated for the selective removal of CO2 from the CO2−CH4 gas mixture. Experiments were carried out to evaluate the effectiveness of different membrane modules and different solvents for the removal of CO2 from a gas mixture containing 10% CO2 and 90% CH4. Three different membrane modules with fibers made from polypropylene, super phobic polypropylene, and silicone rubber were used in this study. The effects of gas and liquid flow rates, temperature, solvent type and concentration, and membrane module type were investigated. The experimental results indicated that CO2 removal increased with increasing the liquid flow rate, decreasing gas flow rate, and increasing solvent concentration. For physical absorption, the CO2 removal decreased with increasing temperature, whereas temperature had negligible effect using chemical absorption. The polypropylene module showed the best performance in terms of CO2 flux.

Evaluation of a mathematical model using experimental data and artificial neural network for prediction of gas separation

In recent times, membranes have found wide applications in gas separation processes. As most of the industrial membrane separation units use hollow fiber modules, having a proper model for simulating this type of membrane module is very useful in achieving guidelines for design and characterization of membrane separation units. In this study, a model based on Coker, Freeman, and Fleming's study was used for estimating the required membrane area. This model could simulate a multicomponent gas mixture separation by solving the governing differential mass balance equations with numerical methods. Results of the model were validated using some binary and multicomponent experimental data from the literature. Also, the artificial neural network (ANN) technique was applied to predict membrane gas separation behavior and the results of the ANN simulation were compared with the simulation results of the model and the experimental data. Good consistency between these results shows that ANN method can be successfully used for prediction of the separation behavior after suitable training of the network.

Impacts of coagulation pretreatment on MF filtration and a comparative study of different membrane module types

Changes in the regulatory requirements and the forthcoming Disinfectant/Disinfection By-Products (D/DBP) Rule will require that drinking water treatment facilities be operated to achieve maximum removals of particles and disinfectant tolerant microorganisms as well as natural organic matter (NOM). For drinking water production, the use of membrane filtration processes such as microfiltration and ultrafiltration (MF/UF) alone to satisfy the turbidity, particle and microorganism removal a requirement of the surface water treatment regulation (SWTR) is not enough. MF/UF treatment processes can achieve only nominal (10 percent) removal of disinfection by-products (DBP) precursors (James, et al., 1995). On the other hand, too fast fouling can make the filtration processes more difficult to carry on. To solve these problems, many authors have been interested in installing coagulation pretreatment before membrane filtration to improve membrane performance. However, previous studies reported conflicting results. Some supported the effectiveness of coagulation pretreatment, while others contended that coagulation aggravated membrane performance. This research aims to identify the effects of coagulation pretreatment on membrane filtration through a pilot study using PVDF membrane in combination with analyzing the rationale of coagulation. Another objective of this research was to evaluate the different impacts on membrane performance of using different membrane modules (the submerged module and pressured module). The results showed that coagulation pretreatment greatly improved the membrane performance, extending the filtration time as well as reducing the permeated organic level, and that the submerged module is much more efficient than the pressured module.

Enhancement of membrane permeability by gas-sparging in submerged hollow fibre ultrafiltration of macromolecular solutions: Role of module design

Permeability in membrane filtration processes suffers from two major limiting factors: concentration polarization and membrane fouling. Gas-sparging, which involves bubbling of a gas in close proximity of a membrane, is known to minimise both of these. Gas-sparged membrane filtration is carried out either by pressurising a gas-sparged feed side or by using suction to draw the permeate through a membrane from the un-pressurised, gas-sparged feed side. The first approach is mainly used in ultrafiltration processes. The second approach which is easier to implement and is widely used in microfiltration processes. This paper discusses the enhancement of permeability by gas-sparging in suction-driven, submerged hollow fibre ultrafiltration using two different membrane module types. These modules were prepared using hollow fibre membranes having nominal MWCO of 150 kDa and were used to ultrafilter polysaccharide solutions. Depending on the operating conditions and on the module design, gas-sparging enhanced effective hydraulic permeability by as much as 115%. The extent of membrane fouling was also significantly lower in the gas-sparged mode. The effectiveness of gas-sparging was found to be greater with one membrane module type, clearly highlighting the effect of module design on process efficiency.

New options for achieving regulatory compliance with low-pressure membranes

Protection against chlorine resistant pathogens, and Cryptosporidium in particular, has become a critical issue for water purveyors. For plant retrofits, ozone and more recently ultraviolet (UV) light technologies, are considered cost-effective solutions to provide an additional barrier to pathogens. The membrane filtration technology is, however, rapidly evolving and both costs and system recoveries are consistently improving. By physically removing microorganisms membrane filtration avoids the formation of disinfection by-products (DBPs) and the need to address changing target pathogens. This paper will present data collected using a novel pilot which evaluates the custom design approach and allows multiple types of membrane modules to be evaluated within a single pilot unit. Pilot testing was performed at the Marden Water Treatment Plant, in Sheboygan, North Shore, and Green Bay, Wisconsin, during 2000 and 2001. An analysis, based on data generated during these pilot tests, will be presented that shows that granular media filter boxes can be rehabilitated with membrane filtration and increase filtration capacity by at least 15%. This engineering analysis includes evaluation of specific aspects of the process including filtration mode, flux, backwashing, the layout of the existing facilities, the potential to reuse existing equipment, and cost comparisons with proprietary membrane systems.

Automation and process control of reverse osmosis plants using soft computing methodologies

At a time of intensive demand for producing fresh water at a reasonable cost, addressing automation, process control and cost optimization of desalination plants have become increasingly evident. Large-scale direct seawater reverse osmosis (RO) plants must perform at high standards due to the increasing cost of high quality water production, high equipment utilization, and rising government regulations on labor protection and the environment. In this keynote presentation, the recent innovation and technological advances in the design and implementation of soft computing methodologies for desalination processes are addressed. Such advances are mainly due to the recent developments of intelligent control design approaches for the integration of sensory information, computation, human reasoning and decision making. The principal partners in such an intelligent system include fuzzy logic (FL), neural network (NN), generic algorithms (GA) and probabilistic reasoning (PR). Various issues which is related to the design and implementation of soft computing methodologies including the trade-off between tolerance, precision and uncertainty are also addressed. As a case study, the design and implementation of an intelligent system for a direct seawater RO system located near Atlantic Ocean at Boca Raton, Florida is presented. The operation of the prototype plant indeed demonstrated the effective and optimum performance of the design for two types of membrane modules, spiral wound (SW) and hollow fine fiber (HFF), under forced diverse operating conditions. The system has achieved a constant recovery of 30% and salt passage of 1.026% while salt concentration of six major salts were kept below their solubility limits at all time. The implementation of the proposed intelligent control methodology has achieved a 5% increase in availability and reduction in manpower requirements as well as reduction in overall chemical consumption of the plant. Therefore, it is believed that the cost of producing water can be decreased using the proposed fully automated control strategy.